This invention pertains to a thermally processable imaging element, and in particular to a thermally processable imaging element incorporating an ion exchanged reducing agent.
It is well known in the art that the introduction of photographically useful compounds, such as photographic developers, couplers, development inhibitors, electron transfer agents, base precursors, fixing agents, i.e., ligand capable of binding silver, silver stabilizing agents and the like, into photographic, thermographic and photothermographic elements can lead to premature reaction of the photographically useful compound with the other components of the imaging element. For example, placing conventional color developers, such as p-phenylenediamines and p-aminophenols, into sensitized photographic or photothermographic elements leads to desensitization of the silver halide emulsion and unsuitable fog. Much effort has therefore been directed at trying to produce effective blocked developers, which can be introduced in silver halide emulsion elements without deleterious desensitization or fog effects and which unblock chemically under conditions of development so that developer is free to participate in color forming (dye forming) reactions.
U.S. Pat. No. 3,342,599, to Reeves, discloses the use of Schiff base developer precursors. U.S. Pat. No. 4,157,915, to Hamaoka et al., and U.S. Pat. No. 4,060,418, to Waxman and Mourning, describe the preparation and use of carbamate blocked p-phenylenediamines. Color developing agents having xcex1-ketoacyl blocking groups are described in U.S. Pat. No 5,019,492.
All of these approaches and inventions have failed in practical product applications because of one or more of the following problems: desensitization of sensitized silver halide; unacceptably slow unblocking kinetics; instability of blocked developer yielding increased fog and/or decreased Dmax after storage; and the requirement of a dinucleophile, such as hydroxylamine, to initiate developer release.
There has been a need for a thermally processable imaging element incorporating a a reducing agent, which is stable until development. Then, the element can be developed rapidly and easily.
These and other needs have been satisfied by providing photothermographic and thermographic imaging elements comprising polymers with ion exchangeable groups (ionomers, polyesterionomers, and ion-containing latices) which limit diffusion of a reducing agent under coating conditions. The immobilization of a reducing agent prevents interaction with the imaging layer of thermally processable imaging element under storage conditions. The reducing agent can be released from the ion exchange polymer by raising the temperature to at least 50xc2x0 C.
One aspect of the invention comprises a thermally processable imaging element comprising at least one thermally processable imaging layer on a support, wherein the imaging element also comprises at least one reducing agent ionically bound to an ion exchange matrix. The imaging element is preferably a photothermographic element comprising an imaging layer comprising a light sensitive silver halide, an oxidizing agent, and a reducing agent.
Another aspect of this invention comprises a method of developing the above-described thermally processable imaging element which comprises heating the element to a temperature of at least about 50xc2x0 C.
Still another aspect of this invention comprises a method of imaging comprising the steps of:
forming an image in an imagewise exposed and thermally processed photothermographic element comprising a thermally processable imaging layer and containing a reducing agent ionically bound to an ion exchange resin; said method comprising the steps of:
scanning said formed image to form a first electronic image representation from said formed image;
digitizing said first electronic image to form a digital image;
modifying said digital image to form a second electronic image representation; and
transforming, storing, transmitting, printing or displaying said second electronic image representation.
A further aspect of this invention comprises a method of forming an image comprising the steps of:
forming an image in an imagewise exposed photothermographic element comprising a thermally processable imaging layer and containing a reducing agent ionically bound to an ion exchange resin;
scanning said formed image to form an electronic image representation from said formed image; and
transforming, storing, transmitting, printing or displaying said electronic image representation.